Sorry I missed this post.....
The M100 A Frame is similar, but as pointed out different in so much as the cut out on the reinforcing insert.
Below are the A frame rails built by Dale, also a pic of the M100 A-frame reinforcing rails.
I built my A-frames too and they fit.
As for the distance out......It's not possible for me to give you that answer at the moment as mine is stripped down, however, if the rails are made to the correct length, they will meet up with the casting at the correct angle and be attached to the casting.
It appears that the casting is the same or similar to the MBT or T3.
Drawings are here...... http://www.jeepdraw.com/trailer.htm
See....... Willys MBT, Bantam Trailer A-Frame Braces and Reinforcing Inserts (Pics on JeepDraw Home Page) MBT-A-FM.pdf
Pic of the inserts I made.
Hey Bill.......remember the fun we had after I made the handbrake lever, laying it up against originals to see if anyone could pick it was a home made thing ?
Those were the days mate